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Linux/fs/binfmt_script.c

  1 /*
  2  *  linux/fs/binfmt_script.c
  3  *
  4  *  Copyright (C) 1996  Martin von Löwis
  5  *  original #!-checking implemented by tytso.
  6  */
  7 
  8 #include <linux/module.h>
  9 #include <linux/string.h>
 10 #include <linux/stat.h>
 11 #include <linux/binfmts.h>
 12 #include <linux/init.h>
 13 #include <linux/file.h>
 14 #include <linux/err.h>
 15 #include <linux/fs.h>
 16 
 17 static int load_script(struct linux_binprm *bprm)
 18 {
 19         const char *i_arg, *i_name;
 20         char *cp;
 21         struct file *file;
 22         char interp[BINPRM_BUF_SIZE];
 23         int retval;
 24 
 25         if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))
 26                 return -ENOEXEC;
 27 
 28         /*
 29          * If the script filename will be inaccessible after exec, typically
 30          * because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give
 31          * up now (on the assumption that the interpreter will want to load
 32          * this file).
 33          */
 34         if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
 35                 return -ENOENT;
 36 
 37         /*
 38          * This section does the #! interpretation.
 39          * Sorta complicated, but hopefully it will work.  -TYT
 40          */
 41 
 42         allow_write_access(bprm->file);
 43         fput(bprm->file);
 44         bprm->file = NULL;
 45 
 46         bprm->buf[BINPRM_BUF_SIZE - 1] = '\0';
 47         if ((cp = strchr(bprm->buf, '\n')) == NULL)
 48                 cp = bprm->buf+BINPRM_BUF_SIZE-1;
 49         *cp = '\0';
 50         while (cp > bprm->buf) {
 51                 cp--;
 52                 if ((*cp == ' ') || (*cp == '\t'))
 53                         *cp = '\0';
 54                 else
 55                         break;
 56         }
 57         for (cp = bprm->buf+2; (*cp == ' ') || (*cp == '\t'); cp++);
 58         if (*cp == '\0') 
 59                 return -ENOEXEC; /* No interpreter name found */
 60         i_name = cp;
 61         i_arg = NULL;
 62         for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++)
 63                 /* nothing */ ;
 64         while ((*cp == ' ') || (*cp == '\t'))
 65                 *cp++ = '\0';
 66         if (*cp)
 67                 i_arg = cp;
 68         strcpy (interp, i_name);
 69         /*
 70          * OK, we've parsed out the interpreter name and
 71          * (optional) argument.
 72          * Splice in (1) the interpreter's name for argv[0]
 73          *           (2) (optional) argument to interpreter
 74          *           (3) filename of shell script (replace argv[0])
 75          *
 76          * This is done in reverse order, because of how the
 77          * user environment and arguments are stored.
 78          */
 79         retval = remove_arg_zero(bprm);
 80         if (retval)
 81                 return retval;
 82         retval = copy_strings_kernel(1, &bprm->interp, bprm);
 83         if (retval < 0) return retval; 
 84         bprm->argc++;
 85         if (i_arg) {
 86                 retval = copy_strings_kernel(1, &i_arg, bprm);
 87                 if (retval < 0) return retval; 
 88                 bprm->argc++;
 89         }
 90         retval = copy_strings_kernel(1, &i_name, bprm);
 91         if (retval) return retval; 
 92         bprm->argc++;
 93         retval = bprm_change_interp(interp, bprm);
 94         if (retval < 0)
 95                 return retval;
 96 
 97         /*
 98          * OK, now restart the process with the interpreter's dentry.
 99          */
100         file = open_exec(interp);
101         if (IS_ERR(file))
102                 return PTR_ERR(file);
103 
104         bprm->file = file;
105         retval = prepare_binprm(bprm);
106         if (retval < 0)
107                 return retval;
108         return search_binary_handler(bprm);
109 }
110 
111 static struct linux_binfmt script_format = {
112         .module         = THIS_MODULE,
113         .load_binary    = load_script,
114 };
115 
116 static int __init init_script_binfmt(void)
117 {
118         register_binfmt(&script_format);
119         return 0;
120 }
121 
122 static void __exit exit_script_binfmt(void)
123 {
124         unregister_binfmt(&script_format);
125 }
126 
127 core_initcall(init_script_binfmt);
128 module_exit(exit_script_binfmt);
129 MODULE_LICENSE("GPL");
130 

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